Date: Tue, 4 Jun 2013 08:30:47 -0700 From: Larry Melia <larrymelia@gmail.com> To: freebsd-virtualization@freebsd.org, Alexander Motin <mav@freebsd.org>, KY Srinivasan <kys@microsoft.com>, "Abhishek Gupta (LIS)" <abgupta@microsoft.com> Subject: more granular detection and control to disable/enable PCI-ATA devices Message-ID: <CADFB2gzUFvKSy9=t5CwVKXvF0XHwUP3rBxXOp3ii0kQW4anC5g@mail.gmail.com>
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Hi Alexander- With you suggestions, I finally was able to get the override driver working-see https://github.com/FreeBSDonHyper-V/freebsd-snapshot/blob/hyperv-dev-ata-override/sys/dev/hyperv/stordisengage/hv_ata_pci_disengage.c. While it operates wonderfully, allowing our "enlightened" driver to improve performance, some versions of Hyper-V still use the native CD-ROM driver, because there is no "enlightened" support for it in the hypervisor. From my limited knowledge of the ATA drivers, it seems likely that the PCI-ATA driver be attached when a CD-ROM is detected, but lower-level drivers disabled (during a probe) when a hard drive is detected. On Hyper-V, therefore, a user would be able to configure a PCI/IDE virtual controller with two devices, the first device a hard disk and the second one a CD-ROM. The CD-ROM would operate via the native driver, whereas the hard disk would use the "enlightened" driver (to improve performance). Is there an easy way to add more granular detection, disabling the native ATA driver(s) selectively for hard drives, while allowing CD-ROM devices to be natively attached? Any suggestions would be very much appreciated. -Larry
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